Giant babax (Babax Waddelli) helpers cheat at provisioning nestlings in poor conditions

In cooperatively breeding species, helpers take higher risks of getting
lower return of investment than breeders due to the incongruity between
helping and breeding. Helpers can deal with the risk by curtailing their
investment or, if possible, claiming immediate rewards in the cooperation.
Given breeders may rely largely on the aid of helpers to raise their
offspring, it can be hypothesized that helpers are more likely to make
adaptive responses to the incongruity-associated risk in adverse habitats
than in good ones. This hypothesis was tested in the giant babax (Babax
waddelli) by comparing helpers' provisioning behaviors between two
breeding populations in adverse high-altitude and good low-altitude
environments. These two populations differed significantly in their egg
size and nestlings’ growth patterns. Helpers in both populations made
great contributions to the raising of offspring. During provisioning,
helpers in the high-altitude population exhibited significantly higher
feeding rates but delivered fewer insects per feeding bout than their
counterparts in the low-altitude population. Helpers in both populations
displayed a cheating strategy of 'non-feeding' to reduce
investment in provisioning. They pursued immediate excess rewards via
kleptoparasitism of nestling fecal sacs in the high-altitude population
but not in the low-altitude one. Accordingly, breeders made different
antagonistic actions toward the cheating helpers between populations. Our
findings confirm that helpers are prone to deceiving cooperation under
poor breeding conditions and that breeders' tolerance of the cheating
behavior of helpers is determined by their dependence on the helpers'
aid.